This invention relates generally to the field of data storage devices, and more particularly, but not by way of limitation, to incorporation of a tubular gasket in a disc drive.
Disc drives are used for data storage in modem electronic products ranging from digital cameras to computers and network systems. Typically, a disc drive includes a mechanical portion, or head disc assembly (HDA), and electronics in the form of a printed circuit board assembly (PCB), mounted to an outer surface of the HDA. The PCB controls HDA functions and provides a communication interface between the disc drive and a host being serviced by the disc drive.
Typically, an HDA includes a magnetic disc surface affixed to a spindle motor assembly for rotation at a constant speed and an actuator assembly positionably controlled by a closed loop servo system. The actuator assembly supports a read/write head that traverses generally concentric magnetic tracks radially spaced across the disc surfaces for writing data to and reading data from the magnetic tracks.
Continued demand for disc drives with ever-increasing performance capabilities insists manufacturers seek ways to increase the storage capacity, data throughput and to improve overall operating efficiencies. Present generation disc drives typically achieve bit densities of multiple gigabits per square centimeter, Gbits/cm2. Increasing bit densities can be achieved by increasing the number of bits stored along each track, or bits per inch (BPI), generally requiring improvements in the read/write channel electronics, and/or by increasing the number of tracks per unit width, or tracks per inch (TPI), generally requiring improvements in servo control systems. As bit density increases it is not uncommon for fly heights to decrease, which heighten the need to control environmental conditions internal to the disc drive.
One approach taken by disc drive manufacturers to improve control of the internal environment has been the inclusion of pre-formed gasket material sandwiched between housing components, which precludes passage of external environmental conditions into the disc drive. For example, U.S. Pat. No. 4,896,231 issued to Hoppe exemplifies one such construction of a pre-formed gasket recently proposed in the art, sealing the inner workings of the disc drive from its external environment. The Hoppe solution includes a central stiffener member sandwiched between a pair of foam layers. Typically, pre-formed gaskets, either single or multi layered, are punched from sheets of gasket material that produce highly functional gaskets but also large volumes of waste material. Additionally, multiple product lines normally means multiple configurations of gaskets to be purchased, transported, received and inspected then stocked and issued to production. These material management costs can easily overshadow the cost of the gasket itself.
An alternate approach is exemplified by U.S. Pat. No. 5,326,611 issued to Kishita et al, which proposes the use of a fluorosilicone rubber composition injected on a surface of one of either housing components of the disc drive. Other known approaches incorporate the use of formed-in-place silicone rubber gaskets. However, a characteristic common to both materials is their propensity to out-gas volatiles that remain within the material subsequent to the cure process. Out-gassing, even at a significantly reduced rate, directly impacts head-disc interface, deteriorating fly height and is known to lead to stiction and has led to head crashes. Additionally, the cure process the formed-in-place gasket subjects the housing component to elevated temperatures that can warp the housing component, causing the housing component to be scraped.
As such, challenges remain and a need persists for improved materials and techniques for providing gaskets that are cost effective and maintain the internal environment of a disc drive.
Embodiments of the present invention provide a head disc assembly comprising having a basedeck with a threaded attachment aperture supporting a rotatable disc surface for storage and retrieval of data and a rotary positionable read/write head adjacent the rotatable disc surface for writing data to and reading data from the rotating disc surface, the basedeck communicating with a top cover that includes a mating aperture aligned to the threaded attachment aperture to form an enclosure while providing a gasket groove with an overlapping portion forming a gasket junction adjacent the top cover.
The gasket groove supports a tubular gasket that has a first end, a second end and a main body portion. The tubular gasket is nestled into the gasket groove and sandwiched between the top cover and the basedeck. The first end of the tubular gasket is adjacent the overlapping portion of the gasket groove and the second end of the tubular gasket is likewise adjacent the overlapping portion. However, the second end turns to communicate with the main body portion to seal the enclosure when the top cover is secured to the basedeck with a top cover fastener by passing the top cover fastener passing through the mating aperture into threading engagement with the threaded attachment aperture, then applying a torque at a predetermined level, a sealed environment within the enclosure is formed.
These and various other features and advantages, which characterize embodiments of the present invention, will be apparent from the reading of the following detailed description and review of the associated drawings.